Electric-motor drive.



K. A. PAULY.

ELECTRIC MOTOR DRIVE.

APPLICATION FILED 11110.29, 191s.

1,089,783. Patnted Mar.10,1914.

WTTNESSES JNYENTUH .KZHHL .131 Pa ULII;

' H25 Arranzvzx TfivIirEI) STATES PATENT OFFICE.

KARL A. PAULY, OF

SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, ACORPORATION OF NEW YORK.

ELECTRIC-MOTOR DRIVE.

Specification of Letters Yatent.

To all whom it may concern Be it known that I, KARL A. PAULY, a citizenof. the United States, residing at Schenectady, county of Schenectady,State of New York, have invented certain new and useful Improvements inElectric-Motor Drives, of which the following is a specification.

My invention relates to electric motor drives and is particularlyapplicableto such drives for machines, driven by a plurality of motorswhich must be reversed, as for instance, universal reversing rollingmills.

A universal rolling mill is one in which a piece of steel can be rolledsimultaneously on all four sides, the mill being equipped with bothhorizontal and vertical rolls. The speeds of the rolls of such, a milldepend upon the reductions produced in the piece of steel in the twosets of rolls and the direction in which it is passing, that is, whetherit is passing through the horizontal rolls first-and then through thevertical rolls, or vice versa. If the reductions, and therefore, thespeeds of the horizontal and vertical rolls could be adjusted for a assand these maintained continuously, eac of the rolls might be driven by amotor the speed of each of which being adjusted once "and for all.Since, however, a mill of this kind is required for a great variety ofproducts, the

relative s eeds of the rolls are required to vary, an furthermore, thespeeds of the rolls must be controlled so that the pieces of sttiel willnot buckle or stretch between the ro ls. i

To this end, my invention has for its object'a novel electric motordrive for such a mill, or for any machine driven by a plurality ofmotors, which' must be reversed.

In accordance with my invention, I provide the machine with a luralityof motors, the speed of one of w ich is arranged to depend upon the loadthereon, and cause the motors to have different relative speeds whentheir direction of rotation is reversed.

Other features of novelty which characterize my invention are pointedout withv particularity in the claims annexed to and forming a partofthis-specification.

For a better understanding of my invention reference may be had to thefollowing description taken .in'connection with the accompan ing drawingin which the single figures ows diagrammatically a universal rollingmill provided with an electric motor drive in accordance with myinvention.

In the drawing, l are horizontal rolls dr ven'by a motor 9, and 8 arevertical rolls driven by a motor 4. The armatures of these motors aresupplied with urrent from any suitable source, as for example, afly-Wheel motor generator set 5 as shown. The field windings of thesemotors may be supplied from the same source as are the armatures, or anyother suitable source. I have shown a motor generator set 6 supplyingthese field windings.

- If a piece of steel 7 enters the horizontal rolls 1 first, then thespeed of the vertical rolls 3 must be higher than that of the horizontalrolls while if the steel enters the vertical rolls first then .the speedof the vertical rolls must be lower than that of the hori-' zontalrolls. Since the maximum reduction usually takes place in the horizontalrolls, the difl'erence in speeds of the horizontal and vertical rolls isusually comparatively slight in the first case, but is usuallyconsiderable in the second case. If the steel enters the horizontalrolls first, the motors 2 and 4 revolve in one direction, while if thesteel enters the vertical rolls first the motors 2 and 4 revolve in theopposite direction. This reversal of the motors is taken care of bysuitable means, as by a reversing or control switch 8 having stationaryand movable. contacts. In order that the rolls will have the relativespeeds referred to above, I cause the motors to have different relativespeeds when their direction of rotation is reversed, preferably bychanging the field strength of one of the motors, as by cutting PatentedMar. 10, 1914.

aresistance intothe circuit of itsfield winding. I also provide one ofthe motors with means for causin its speed to depend upon its load,'preferab y causing it to slow down as the load thereon increases. I mayaccomplish this by means of a field winding sup- 'plied with currentproportional to the armature current and connected accumulatively withrespect to the main field winding on the motor. With the motor drivingthe vertical rolls rovided. with such means, its speed will rop to thenormal value assuming that the vertical rolls are taking a draft whichcalls for full load torque. If the draft is less than that which wouldcall for full load on this motor, the tendency of this motor will betorun at a speed greater than that required and will assist the motor driving the horizontal rolls, the speed of the vertical rolls adjustingitself to that corresponding to full load torque. If the draft of thevertical rolls is such as to require a torque in excess of full loadtorque on the motor 4 driving the vertical rolls, it will slow downbeyond normal and the motor driving the horizontal rolls will assist themotor driving the vertical rolls in forcing the steel between them. Thistransfer of the load from one motor to the other and consequent changeof speed of the .motor driving the vertical rolls will tend topreventany buckling or stretching of the steel between the rolls.

If, under certain conditions which might arise in certain universalrolling mills, there is danger of the vertical rolling mill motor havingsuch an excessive torque as to stretch or buckle the material, thistendency can be reduced to harmless proportions by providing then1otor'2 driving the horizontal rolls with means for causing its speedto depend upon the load on motor 4 driving the vertical rolls, that is,causing the motor 2 to speed up when the load on motor 4 increases. Iprefer to accomplish this by meansof a field windin on the horizontalrolls motor supplied with current proportional to the armaturecurrent ofthe motor driving the vertical rolls and connected difierentially withrespect to the main field winding of the motor driving the horizontalrolls.

Referring to the drawing more in detail,

the fly-wheel motor generator set consists ofa separately excitedgenerator 9, a fly-wheel 10 and induction motor 11. The induction motoris supplied with alternating currentfrom mains 12. An automatic rheostator slip regulator 13 is arranged to cut resistance into or out of therotor circuit of the motor 11, and consists of a slip regulating ortorque motor 14 connected in series with the motor 11 and of a waterrheostat 15, the plates of which are separated or brought together bythe slight motion of the motor 14.

The exciter motor generator set 6 comprises an induction motor 16driving a shunt wound exciter 17 and a series exciter 18. The shuntwound exciter 17 supplies current to the mains 19 to which are connectedthe field windings 20 and 21 of motors 2 and 4, through adjustingrheostats 22 and 23. The field winding of enerator 9 is also connectedto the mains 19 through the reversing switch 8 and an adjusting rheostat24.

The armaturesof motors 2 and 4 are connected in parallel with thearmature of generator 9. The field winding of exciter 18 is connected inseries with the armature of motor 4 so that the voltage generated bythis exciter is directly proportional to the current flowing through thearmature of motor 4, and consequently the load thereon. A field winding25, which is cumulatively connected with respect to field winding 21, isconnected to the armature of exciter 18 through the reversing switch 8and an adjusting rheostat 26. Under certain conditions as explainedabove it may be deemed desirable to supply motor 2 with a field winding27 connected differentially with respect to field winding 20. Thiswinding 27 and an adjusting rheostat 28 are shown as connected inparallel with winding 25 and rheostat 26.

Since the voltage of exciter 18 is proportional to the load on motor 4,and since wind ing 25 on this motor is connected to the brushes of thisexeiter so as to be cumulative with respect to winding. 21, motor 4slows down upon an increase in the load on this motor. Since, winding 27of motor 2 is also connected to the brushes of exciter 18 and so as tobe difi'erential with respect to winding 20, the speed of motor 2 alsodepends upon the load on motor 4, but in such a way'as to increase withthe load on motor 4 instead of decreasing.

I have shown the control switch 8 with four positions forward andfourreverse. WVhen the control switch is in any of the forward positions1, 2', 3 or 4, connections are made so that motors 2 and 4 turn therolls 1 and 3 in such a direction that steel, in order to be rolled,must enter the horizontal rolls first, When the control switch is in anyof the reverse positions 1 2 3 or 4 the motors turn the rolls 1 and 3 inthe opposite direction so that in order to roll the steel, it must enterthe vertical rolls first. The system of control employed is that knownas the Ward Leonard system. The exciter 17 supplies excitation to thegenerator 9, the armature of which supplies current to the motors 2 and4. In order to control the speed of these motors resistance sections 29are inserted by the switch 8 in series with the field windin ofgenerator 9, and in order to reverse tiese motors the potential ofgenerator 9 is reversed by reversing the connections of its fieldwinding with the exciter 17 by the control switch 8.

As explained above, the field windings 20 and 21 of motors 2 and 4,respectively, are connected in parallel across the mains 19 suppliedwith current by exciter 17, and since motor 4 must drive the rolls 8 ata higher relative speed than the rolls 1 are driven when steel entersthe horizontal rolls 1 first, a resistance 30, which is preferablyadjustable, is arranged to be cut into the circuit of field winding 21.This resistance weakens the field of motor 4 when the switch 8 is in anyof the forward positions, and thereby causes the motor 4 to revolve at ahigher speed than motor 2. By making the rheostat 30 adjustable, thespeed of motor 4 may be changed when the motors are running forward ifdesirable because (of a difference in the size, section orcharacteristic ofthe steel to be rolled. But when the steel enters theverticalrolls first, motor 4 must run slower than motor 2, and Itherefore provide the switch 8 with a pair of contacts 31 forshort-circuiting the resistance 30 during all of the reverse positions.

Since the field of exciter 18 is in series with the armature of motor 4,and since the motors are reversed by reversing the direction of thecurrent in their armatures, it is necessary to reverse the connectionsbetween the armature of exciter 18 and the fieldwindings 25 and 27whenthe motors 2 and 4 are reversed, in order that field winding 25 isalways connected cumulatively with respect to field winding 21, wherebymotor 4 slows down when the load thereon increases, and field winding 27is always connected differentially with respect to field vindingQO,whereby motor 2 speeds up when the-loadlon motor 4 increases. The

connections between the armature of exciter 18 and field windings 25 and27 are reversed through the lower four contacts of reversing switch 8 inthe well known manner. Although I have described my invention inconnection with a particular system of rolling mill drive, I desire itto be understood that it is not limited thereto, and may be used in-anysystem of reversing motor drive, and I aim in the appended claims tocover all modifications which do not depart from the spirit and scope ofmy invention.

lVhat I claim as new and desire to secure by Letters Patent of theUnited States, is

1. In combination, a plurality of motors, means for causing the speed ofone of said motors to depend upon the load thereon, means for reversingsaid motors, and means for causing said motors to .have differentrelative speeds when their direction of rotation is reversed.

2."In combination, a lurality of motors, means for causing one of saidmotors to slow down as the load thereon increases, means for reversingsaid motors, and means for causing said motors to have difl'erentrelative speeds when-their direction of rotation is reversed.

In combination, a plurality of motors, means for causing the speed ofone of said motors to depend upon the load thereon,

means for reversing said motors, and means for changing the fieldstrength of one of said motors when its direction of rotation isreversed.

4. In combination, a plurality of motors, means for causing one of saidmotors to slow down as the load thereon increases, means for reversingsaid motors, and 'means for changing the field strength of one of saidmotors when its direction of rotation is re versed.

5. In combination, a plurality of motors, means for causing the speed ofone of said motors to depend upon the load thereon,

.means for reversing said motors, aresistance, and means for cuttingsaid resistance into the field circuit of one of said motors when itsdirection of rotation is reversed.

6. In combination, a plurality of motors, means for causing one of saidmotors to slow down as the load thereon increases, means for reversingsaid motors, a resistance, and

means for cutting said resistance into the field circuit'of one of saidmotorswhen its direction of rotation is reversed.

7. In combination, a plurality of motors, a. separately excitedgenerator supplying the armatures thereof, means for energizing thefield windings of said motors and generator, means for varying the fieldstrength of said generator so as to vary the speeds of-said motors,means for causing the speed of one of said motors to depend upon theload thereon, means for reversing said motors, and means for causingsaid motors to have different relative speeds when their direction ofrotation is reversed.

8. In combination, a plurality of motors,

a separately excited generator supplying the armatures thereof, meansfor energizing the field windings of said motors and generator, meansfor varying the field strength of said generator so as to vary thespeeds of said motors, means for causing one of said motors to slow downas the load thereon increases, means for reversing said motors, andmeans for causing said motors to have different relative speeds whentheir dlrection of rotation is reversed.

9. In combination, a plurality of motors, a separately excited generatorsupplying the arn'iatures thereof, means for energizing the fieldwindings of said motors and generator, means for varying the fieldstrength of said generator so as to vary the speeds of said motors,means for causing the speed of one of said motors to depend upon theload thereon, means for reversing said motors, and means for changingthe field strength of one of said motors when its direction of rotationis reversed.

10. In combination, a plurality of motors, a se iarately excitedgenerator supplying the armatures thereof, means for energizing thefield windings of said-motors and generator, means for varying the fieldstrength of said generator so as to vary the speeds of said motors,means for causing one of said motors to slow down as the load thereonincreases, means for reversing said motors, and means for changing thefield strength of one of said motors when its direction of rotation isreversed.

11. In combination, a plurality of motors, a separately excitedgenerator supplying the armatures thereof, means for energizing thefield windings of said motors and generator,

means for varying the field strength of said generator so as to vary thespeeds of said motors, means for causing one of said motors to slow downas the load thereon increases, means for reversing said motors, aresistance, and means for cutting said resistance into the field circuitof one of said motors when its direction of rotation is reversed.

13. In combination, two motors, means for causing the speed of one ofsaid motors'to depend upon the load thereon, means for causing the speedof the other of said motors to depend upon the load on said firstmentioned. motor, means for reversing said motors, and means for causingsaid motors to have different relative-speeds when their direct on ofrotation is reversed.

14. In combination, two motors, means for causing oneof said motors toslow down as the load thereon increases, means for causing the other ofsald motors to speed up as the load on said first mentioned motorincreases,

means for reversing said motors, and means for causmg said motors tohave dlfierent relative speeds when their direction of rotation isreversed.

15. In combination, two motors, means for causing the speed of one ofsaid motors to depend upon the load thereon, means for causing the speedof the other of said motors to depend upon the load on said firstmentioned motor, means for reversing said motors, and means for changingthe field strength of one of said motors when its direction of rotationis reversed.

16. In combination, two motors, means for causing the speed of one ofsaid motors, to

depend upon the load thereon, means ;for,

causing the speed of the other of saidmotors to depend upon the load onsaid first mentioned motor, means for reversing said motors, aresistance, and means for cutting said resistance into the field circuitof one 0t said 'motors when its direction of rotation is reversed.

17 In combination, two motors, means for causingioneof said motors toslow down as the load thereon increases, means forcau'sing the other ofsaid motors to speed up 'as the load on said first mentioned mot-or1ncreases, means for reversing said motors, and means for changin thefield strength of one of said motors w on its direction of rotation isreversed.

18. In combination, two motors, means for causing one of said motors toslow down as the load thereon increases, means for causing the-other ofsaid motors to. speed up as the load on said first mentioned motorincreases, means for reversing said motors, a resistance, and means forcutting said resistance into the field circuit of one of said motorswhen its direction of rotation is re versed.

19. In combination, two motors, a separately excited enerator supplying,the armatures thereo ,,means for energizing the field windings of saidmotors and generator I means for varying the field strength of saidgenerator so as to vary the speeds ofsaid motors, means for causing oneof said motors to slow down as the load thereon increases, means forcausing the other of said motors to speed up as the load onsaid firstmentioned motor increases, means for reversing said motors, and meansfor causing said motors to have different relative speeds when theirdirection of rotation is reversed.

20. In combination, two 'inotors, a separately excited eneratorsupplying the armatures thereo means 'for energizing the field windingsof said motors algd generator, means for varying the field str ngth ofsaid generator so as to vary the speeds of said motors, means forcausing one of said motors to slow down as the load thereon increases,means for causing the other of said motors-to speed up as the load onsaid first mentioned motor increases, means for reversing said motors,and means for changing the field strength of one of said motors when itsdirection of rotation is reversed.

21. In combination, two motors, a separately excited generator supplyingthe armatures thereof, means for energlzlng the field windings of saidmotors and generator means forv varying thefield strength of salgenerator so as to vary the speeds of said motors,' means for causingone of said motors to slow down as the load thereon in-, creases, meansfor causing the other of said motors to speed up as the load on saidfirst mentloned motor increases, means for reversing said motors, aresistance, and means for cutting said resistance into the field circuitof one of said motors whenits direction of rotatlon is reversed.

22. In combination, two motors, aseparately excited generator supplyingthe armatures thereof, means for energizing the field windings of saidmotors and generator, means for varying the field strength of said genrator so as to vary the speeds of said mo ors, means. for causing one ofsaid mo tors to slow down as the load thereon increases, means forcausing the other of said motors to speed up as the load on said firstmentioned motor increases, means for reversing said motors, anadjustable resistance, and means for cutting said resistance into thefield circuit of one of said motors when its direction of rotation isreversed.

23. In combination, a plurality of motors, means for causing the speedof one of said motors to depend upon the load thereon, means forreversing said motors, an adjustable resistance, and means for cuttingsaid resistance into the field circuit of one of said motors when itsdirection of rotation is reversed.

24. In combination, a plurality of motors, means for'causing one of saidmotors to slow down as the load thereon increases, means for reversingsaid motors, an adjustable resistance, and means for cutting saidresistance'into the field circuit of one of said motors whenv itsdirection of rotation is reversed.

25. In combination, a plurality of motors, a separately excitedgenerator supplying the armatures thereof, means for energizing thefield windings of said motors and generator, means for varying the fieldstrength of said generator so as to vary the speeds of said motors,means for causing one of said motors to slow down as the load thereonincreases, means'for reversing said motors, an'

adjustable resistance, and means for cutting said resistance into thefield circuit of one of said motors when its direction of rotation isreversed.

26. In combination, two motors, means for causingone of said motors toslow down as the load thereon increases, means for causing the other ofsaid motors to speed up as the load on said first mentioned motorincreases, means for reversing said motors, an adjustable resistance,and means for cutting said resistance into the field circuit of one ofsaid motors when its direction of rotation is reversed. v

27. In combination, a plurality of motors having main field windings,one of said motors having a second field winding connectedaccumulatively with respect to said main field winding and supplied withcurrent proportional to the armature current thereof, means forreversing said motors, a resistance, and means for cutting saidresistance into the main field circuit of one of said motors when itsdirection of rotation is re field winding and supplied with currentproportional to the armature current thereof,

means for reversing said motors, an adjustable resistance, and means forcutting said resistance into the main field circuit of one of saidmotors when its direction of rotation is reversed.

29. In combination, a plurality of motors having main field windings,one of said motors having a second field winding connectedaccumulatively with respect to said main field winding and supplied withcurrent proportional to the armature current thereof, a resistance, acontrol switch for reversing said motors and for cutting said resistanceinto the main field circuit of one of said motors when its direction ofrotation is reversed.

30. In combination, a plurality of motors having main field windings,one of said motors having a second fieldwindin'g connectedaccumulatively with respect to said main field winding and supplied withcurrent pro portional to the armature current thereof, an adjustableresistance, a control switch for resistance into the main field circuitof one of said motors when its direction of rotation is reversed.

31. In combination, two motors having main field windings, one of saidmotors having a second field winding connected-accumulatively withrespect to its main field winding and supplied with current proportionalto the armature current thereof, the other of said motors having asecond field winding connected differentially with respect to its mainfield winding and supplied with current proportional to the armaturecurrent of said first mentioned motor, means for reversing said motors,a resistance, and means for cutting said resistance into the main fieldcircuit of one of said motors when its direction of rotation isreversed.

32. In combination, two motors having main field windings, one of saidmotors having a second field winding connected accumulatively withrespect to its main field winding and supplied with current proportionalto the armature current thereof, the other of said motors having. asecond field winding connected difierentially with respect to its mainfield winding and supplied with current proportional to the armaturecurrent of said first mentioned motor, means for reversing said motors,an adjustable resistance, and means for cutting said resist ance intothe main field circuit of one of said motors when its direction ofrotation is reversed. c

33. In combination, two motors having main field windings, one of saidmotors having a second field winding connected accumulatively withrespect to its main field winding and supplied with current proportionalto the armature current thereof, the

reversing said motors and for cutting said I other of said motors havinga second field winding connected differentially with respect to its mainfield winding and supplied with current proportional to the armaturecurrent of said first mentioned motor, a resistance, and a controlswitch for reversing said motors and for cutting said resistance intothe main field circuit of one of said motors when its directionofrotation is reversed.

34. In combination, two motors, having main field windings, one of saidmotors having a second field winding connected accumulatively withrespect to its main field winding and supplied with currentproportionalto the armature current thereof, the

other of said motors having a second field winding connecteddifferentially with respect to its main field winding and supplied withcurrent proportional to the armature current of said first mentionedmotor, an adjustable resistance, and a control switch for reversing saidmotors and for cutting said resistance into the main field circuit ofone of said motors when its direction of rotation is reversed. j Inwitness whereof, I- have hereunto set my hand this 28th day of August1913.

KARL A. PAULY. Witnesses:

BENJAMIN B. HULL, MARGARET E. WOOLLEY.

